A 49-year-old male presented to our emergency department with sudden anterior chest pain. His electrocardiogram revealed ST-segment elevations in leads II, III and aVF. An inferior acute myocardial infarction was suspected. Emergent coronary angiography (CAG) showed there was a long lesion in the right coronary artery (RCA), which continued from the proximal to the distal part of RCA with 50% stenosis and narrowed further to 99% stenosis at the distal end. Intravascular ultrasound (IVUS) examination demonstrated a diffuse intramural hematoma raging from the proximal to the distal part of the RCA. No visualization of the intimal flap was identified by IVUS, indicating coronary artery dissection as a pathogenesis of this hematoma formation. After intracoronary injection of isosorbide dinitrate, the 99% stenosis regressed to 50% spontaneously. Neither balloon angioplasty nor stenting was performed. He was discharged home free from symptoms 9 days after the procedure. Thirty-day follow-up CAG revealed an almost normal finding of the RCA and IVUS delineated a complete restoration of the intramural hematoma.